The Geritol solution is the name given to one of the possible direct action methods for reducing the amount of carbon dioxide in the atmosphere, and thus slowing down or reversing global warming.

The oceans are a great natural sink of greenhouse gases. It has been estimated that they absorb 40% of fossil fuel emissions. The key to this is the plankton processing vast stores of gases, how much is unclear. It is known that during the ice ages, carbon dioxide levels dropped 30%.

The question is how can this be done today. In theory, lowering carbon dioxide levels should lower temperatures.

Give me half a tanker full of iron, and I'll give you another ice age.
--John Martin (Moss Landing Marine Laboratory, California)

In the polar regions there are huge reserves of nitrates and phosphates that phytoplankton thrive on. The only thing lacking is iron.

First proposed by Martin in 1998, the Geritol solution would be to seed these oceans with iron dust which then dissolves into the water. It is possible that this is what caused the ice ages: as the land dried more dust blew into the oceans fostering growth of plankton.

In 1996 the idea was tested by the U.S. government. Near the Galapagos Islands exists a fairly biologically barren area. Over a 28 square mile area of blue sea, scientists poured 990 pounds if iron during a week of testing. The waters immediately bloomed green with phytoplankton. At its height, it covered 200 square miles. One thousand pounds of iron dust stimulated over 2000x its own weight in plant growth - much greater than any land fertilizer. The plankton itself soaked up carbon dioxide, reducing the concentration in nearby sea water by 15%. This deficiency in the sea water was quickly made up by drawing carbon dioxide from the air.

If carried out in a full scale, this would only affect 16% of the ocean area. Estimates place it at reducing atmospheric carbon dioxide levels from 6% to 21%.

Its primary advantages are that it is low tech, and simple to stop. Its not hard to dump millions of tons of iron dust into the ocean. If you stop feeding the plankton, the current crop will die.

Questions remain about how much of the carbon dioxide actually gets deeply buried and how this would affect the food chain.